Pressure independent control valve

ABSTRACT

The invention provides valves of the type employing a differential pressure regulator and a characterized valve with a mechanism to enhance control of fluid flow independently of system pressure. The valves of the invention are especially suitable for HVAC applications, and provide operation with improved accuracy over a greater flow range with a reduced risk of hunting. In one preferred aspect, the invention provides improvements by the employment in the differential pressure regulator of a diaphragm with a cup arranged to provide a small leakage, thereby dampening the response of the regulator. In another aspect, a baffle is provided to protect the downstream side of a control disk forming part of the differential pressure regulator.

CROSS REFERENCE TO RELATED APPLICATIONS

The invention pertains to a pressure independent valve of the typedescribed by the present applicant in and U.S. patent application Ser.No. 10/948,662, filed Sep. 23, 2004, which is a divisional of U.S.Patent Application No. 10/049,730, now U.S. Pat. No. 6,827,100. Thisinvention has been described in Disclosure Document No. 541,997 and U.S.Provisional Patent Application No. ______, of the same title, filed Jul.30, 2004, and priority to this Provisional Patent Application is herebyclaimed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention provides valves of the type employing a differentialpressure regulator and a characterized valve with a mechanism to enhancecontrol of fluid flow independently of system pressure. The valves ofthe invention are especially suitable for HVAC applications, and provideoperation with improved accuracy over a greater flow range with areduced risk of hunting.

2. Description of Prior Art Related to the Invention

In HVAC plants, water distribution can be accomplished at constant orvariable flow. Each type of distribution system has advantages anddisadvantages. Today, variable flow systems using electronic 2-waycontrol valves have become generally accepted as the industry standarddue to their benefits, mainly reduced pumping cost achieved as a resultof reducing pump head and flow.

However, a significant disadvantage with many systems in place today isthat balancing the system is a time consuming and costly effort. Thebalancing procedure dictates the quality of the system and requireshighly skilled technicians and tools. According to a typical system flowdesign, each control valve requires a balancing valve to adjust thehydronic circuit with all control valves must be in their open position.Then, as soon as the system is running, depending on different coolingor heating load requirements in the building, valves begin closing andopening. Each opening or closing dynamically alters system pressure, andbalancing these systems becomes time consuming and can only beapproximate.

If terminals are added to a typical system, the whole system requiresrebalancing because some existing terminals must be throttled back. Thisis especially a problem where floors are periodically remodeled and theuses are varied. Wherever the uses change, balancing of the whole systemis required. Moreover, a building is typically running under designconditions only a small of the time. The rest of the time, the hydronicsystem needs to provide an average load of only about 50%. This can meanthat flow is reduced to only about 20%, and differential pressuresacross control valves increase. Since the CV-rating of the valve istypically sized for design conditions, the valve authority decreases andthe modulating valve is downgraded to one acting open or closed only.This makes hunting expected.

Control circuits are interactive. Therefore, when one control valvecloses in a system of the type described above, the differentialpressures on other circuits increases and the associated control valvesmust close to compensate. So when one or more loops become unstable,control problems can spread to other control valves.

In typical current cooling systems, if flow is higher than required, thetemperature differential of the fluid (ΔT) will decrease and result in acooling plant with lower return temperatures to the chiller and reducethe efficiency. If one chiller cannot run at peak efficiency, it is morelikely that the next chiller in a series will be forced to start soonerthan required causing additional electricity and maintenance costs. Theopposite happens in a condensing boiler where a higher returntemperature can avoid the condensing process when the dew point of theexhaust gases cannot be achieved. The same phenomenon can happen incoils. In a heating coil for instance, overflow will result in a lowerΔT and decrease the coil's performance which can result in discomfortdue too a low room temperature.

Significant developments in HVAC valves have been made in the recentpast with the provision of characterized valves, in general, andparticularly of the pressure independent variety. Because of theseimprovements, many of the disadvantages of variable flow systems arelargely eliminated for most HVAC-applications. The valves now availablefor HVAC applications include characterized openings where the degree ofopening movement is proportional to flow rate. U.S. Pat. No. 6,039,304,to Carlson, et al., describes a ball valve with modifiedcharacteristics. The valve includes a disk for characterizing flow topermit a proportional of opening of the valve to correspond to apredetermined flow rate. These valves can provide essentially “equalpercent” characteristics, as well as other flow characteristics, and arecommercially available under the identifier of CCV. They employ a diskhaving a shaped opening with one side shaped to conform to the shape ofthe exterior of the ball or plug. The disk fits inside the port at theseat area, and is secured by a ring. The ability of a valve to provide aflow rate proportional to the movement of a valve actuator is of greatadvantage when manufacturing and installing both valves and theactuators.

It is also important for HVAC and other applications that control valveshave the ability to maintain a constant flow rate despite pressurefluctuations in the system. Valves having this capability are nowavailable. In U.S. Pat. No. 6,827,100, to Carlson, there is described apressure independent control valve, which enables an HVAC operator toset flow rates for any of a plurality of zones and have the selectedrates remain constant independent of variations in pressure due tovariations in heat transfer demand in the several zones. These valvesare commercially available under the identifier of PICCV. Pressureindependent control valves of the type described in U.S. Pat. No.6,827,100 work well over the greater part of their rated nominal flow;however, at certain pressures and flow rates, there is sometimes,especially in closed systems, a risk of oscillation.

At part-load, for instance, when a PICCV with a nominal flow of 10 GPMoperates at 3 GPM, a flow of 3 GPM is maintained, and these valvesprovide good control with no adverse hunting. However, at higher flowrates in closed systems, oscillation can be a problem. While theproblems can be addressed by providing a wide range of valve sizes andselecting valves always having an effective range, so that there wouldalways be one that worked at the problem flow rates and pressures, itwould be desirable to control the problem more directly and enable asmaller range of valve sizes to accomplish the same tasks.

There is a present need for means having the capability to simply andeffectively modifying pressure independent control valves to enable toenhance control of fluid flow independently of system pressure withimproved accuracy over a greater flow range with a reduced risk ofhunting.

SUMMARY OF THE INVENTION

It is an object of the invention to provide improvements for pressureindependent control valves of the type employing a differential pressureregulator and a characterized valve to enhance control of fluid flowand/or improve system stability independently of system pressure and/orflow rate.

It is an object of the invention to provide improvements for pressureindependent control valves of the type employing a differential pressureregulator and a characterized valve to enhance control of fluid flowindependently of system pressure.

It is another object of the invention to provide improvements forpressure independent control valves of the type employing a differentialpressure regulator and a characterized valve to enable operation withimproved accuracy over a greater flow range with a reduced risk ofhunting.

In a preferred aspect, the invention provides improvements for pressureindependent control valves of the type employing a differential pressureregulator and a characterized valve to enhance control of fluid flowindependently of system pressure by the employment in the differentialpressure regulator of a diaphragm with a cup arranged to provide a smallleakage, thereby dampening the response of the regulator.

In another preferred aspect, the accuracy at higher flow rates ofpressure independent valves of the type employing a differentialpressure regulator and a characterized valve to enhance control of fluidflow independently of system pressure by providing a baffle to protectthe downstream side of a control disk forming part of the differentialpressure regulator.

According to one embodiment, a pressure independent fluid flowregulating valve providing a substantially constant flow rate for eachset position, comprises: a flow passage leading to a characterized valvehaving an inlet from and an outlet to said flow passage; upstream ofsaid characterized valve, a seat orifice intersecting said flow passage;a moveable assembly, comprising a disk connected to by a stem, andoperated by a pressure sensing means; wherein the disk is locateddownstream of the seat with which it interacts to vary the flowresistance, and the effective surface area of the disk is essentiallythe same as the effective surface area of said pressure sensing means;downstream of the disk, a baffle is mounted in a fixed position, closeto the disk but at a distance permitting the movement of the disk; thepressure sensing means operates inside a cylinder or chamber which itdivides in two portions, wherein one portion is connected to the inlet,and the other portion is connected via reference pressure passage to apoint downstream of the characterized valve; and spring means forbiasing said moveable assembly.

According to another embodiment, a pressure independent fluid flowregulating valve providing a substantially constant flow rate for eachset position, comprises: a flow passage leading to a characterized valvehaving an inlet from and an outlet to said flow passage; upstream ofsaid characterized valve, a seat orifice intersecting said flow passage;a moveable assembly, comprising a disk connected to by a stem, apressure sensing means comprising a diaphragm and a cup positioned overand covering the pressure sensing means; wherein the disk is locateddownstream of the seat with which it interacts to vary the flowresistance, and the effective surface area of the disk is essentiallythe same as the effective surface area of said pressure sensing means;the pressure sensing means operates inside a cylinder or chamber whichit divides in two portions, wherein one portion is connected to theinlet, and the other portion is connected via reference pressure passageto a point downstream of the characterized valve, and the cup includesan opening permitting fluid to flow between the chamber and the pressuresensing means to provide dampening; and spring means for biasing saidmoveable assembly.

According to another embodiment, a pressure independent fluid flowregulating valve providing a substantially constant flow rate for eachset position, comprises: a flow passage leading to a characterized valvehaving an inlet from and an outlet to said flow passage; downstream ofsaid characterized valve, a seat orifice intersecting said flow passage;a moveable assembly, comprising a disk connected to, and operated by apressure sensing means; wherein the disk is located downstream of theseat with which it interacts to vary the flow resistance and theeffective surface area of the disk, is essentially the same as theeffective surface area of said pressure sensing means; downstream of thedisk, a baffle is mounted in a fixed position, close to the disk but ata distance permitting the movement of the disk; the pressure sensingmeans operates inside a cylinder or chamber which it divides in twoportions, one portion is connected to the throttling device, the otherportion via a reference pressure passage connected to a point upstreamof the characterized valve; spring means biases said moveable assembly.

According to another embodiment, a pressure independent fluid flowregulating valve providing a substantially constant flow rate for eachset position, comprises: a flow passage leading to a characterized valvehaving an inlet from and an outlet to said flow passage; downstream ofsaid characterized valve, a seat orifice intersecting said flow passage;a moveable assembly, comprising a disk connected to by a stem, apressure sensing means comprising a diaphragm and a cup is placed overand covering the pressure sensing means; wherein the disk is locateddownstream of the seat with which it interacts to vary the flowresistance, and the effective surface area of the disk is essentiallythe same as the effective surface area of said pressure sensing means;the pressure sensing means operates inside a cylinder or chamber whichit divides in two portions, wherein one portion is connected to theoutlet, and the other portion is connected via reference pressurepassage to a point upstream of the characterized valve, and the cupincludes an opening permitting fluid to flow between the chamber and thepressure sensing means to provide dampening; and spring means forbiasing said moveable assembly.

Additional and preferred features of the invention will be describedbelow with the positions of the different parts as shown in the figures.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be further described and its advantages made moreapparent when the following detailed description of the invention isread in connection with the accompanying drawings, wherein:

FIG. 1 is a schematic cross-sectional view of the improved pressureindependent control valve of the present invention illustrating amongother things a cup covering the upper side of the diaphragm, which workswith a stem and loosely fit center hole to dampen the reaction of theregulator;

FIG. 2 is a schematic cross-sectional view of the same pressureindependent control valve as in FIG. 1, but a baffle is added to thearea on top of the control disk to counteract an effect of rapid fluidflow against the downstream side of a control disk.

FIG. 3 is a schematic cross-sectional view of the same pressureindependent control valve as in FIG. 1, but without the cup and with abaffle with raised edges.

FIG. 4 is a schematic cross-sectional view of the same pressureindependent control valve as in FIG. 3, but with a cup added to the topof the upper side of the diaphragm.

FIG. 5 is a schematic cross-sectional view of the same pressureindependent control valve as in FIG. 4, but with a control disk withraised edges.

FIG. 6 is a schematic cross-sectional view of an alternative solution tothe pressure independent control valve, wherein the control valve isplaced before the pressure regulator and a cup has been placed so itcovers the upper side of the diaphragm of the pressure regulator.

DETAILED DISCUSSION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

The invention is described below with regard to specific embodimentswhich illustrate the arrangement and function of various component partsfor valves of particular interest, but the mechanisms and principals canbe applied by the skilled worker to other arrangements. The inventionprovides both a construction capable of dampening the response of adifferential pressure regulator component of a pressure independentcontrol valve or one to counteract an effect of rapid fluid flow againstthe downstream side of a control disk in valves of this type. The valvesof the invention can provide a characterized valve 10 either upstream ordownstream of a pressure chamber 2 differential pressure regulatorcomponent. The details of the characterized valve 10 form no part of theinvention, and the characterized valve 10 is illustrated hereschematically only. Reference can be had to U.S. Pat. No. 6,039,304, toCarlson, et al., and U.S. Pat. No. 6,827,100, to Carlson, for specificstructures of interest. The disclosures of these patents areincorporated by reference herein, in their entireties.

Referring to FIG. 1, there is shown an improved pressure independentvalve of the present invention. The valve includes an inlet 1 and outlet16. The inlet 1 communicates with a pressure chamber 2, which cancommunicate with a second pressure chamber 6, via a seat 15 in opening15″ and a control disk 8. The control disk 8 is connected to pressuresensing means comprising a diaphragm 4 via a stem 17. The stem 17 has anextension and is guided by a guide post 9. The guide post 9 is attachedto, or a part of the valve body 7. An assembly comprising the controldisk 8, stem 17 and a pressure sensing means comprising diaphragm 4 canmove as one unit such that control disk 8 can move between open andclosed positions as stem is moved by diaphragm 4. A spring 5 is biasingthe assembly. Throughout this description alternative means, such as apiston working in a cylinder or similar pressure sensing means, can beemployed in place of the diaphragm 4.

In the embodiment of FIG. 1, there is provided a cup 3 with a centerhole 18 for the stem 17 to provide dampening and enhance systemstability. The cup 3 is placed over and covers the upper area of thepressure sensing means comprising diaphragm 4. The center hole 18 has adiameter slightly larger than the stem 17, so the play is small and aresistance to a leakage of fluid between the diaphragm 4 and thepressure chamber 2 is created. The exact numerical value of thetolerance is not critical, and is typically large enough to providecontrol force to reach the diaphragm 4. The flow, being less thanimmediate, dampens the reaction of the pressure regulator and leads to amore stable function of the pressure independent valve.

In the embodiment of FIG. 1, a characterized control valve 10 isconnected between the pressure chamber 2 and the outlet 16. The controlvalve 10 can be operated manually or by an actuator 12. The pressure atthe outlet 16 is via a reference channel 11 brought hack to the underside of the diaphragm 4 which is biased by a spring 5.

Turning now to FIG. 2, an alternative embodiment of a pressureindependent valve is shown with all parts identical to the FIG. 1,except that a baffle 13 has been added. The baffle 13 is attached to theguide post 9. The baffle 13 is positioned just slightly above thehighest point of the operating range of the control disk 8.

Under some conditions, jets of fluid are formed around the periphery ofthe control disk 8 as the fluid moves between the control disk 8 and theseat 15 of the differential pressure regulator. These jets can hit thewall of the valve body 7 and bounce back against the top of the controldisk 8. The baffle 13 prevents the jets from impacting the control disk8 so the force balance of the control disk 8 is not influenced. With thebaffle 13 the accuracy of the pressure independent valve is improved,especially at higher flow rates.

Turning to FIG. 3. there is shown a pressure independent valve with allparts identical to the FIG. 1, except no cup 3 has been added and aspecial baffle 20 is used. The special baffle 20 has a peripheral edge(flange) 19 on the perimeter of the baffle 20. The peripheral edge 19faces downward and has an inside diameter slightly larger than thecontrol disk 8. This makes it possible to fit the control disk 8 insidethe edge 19. This protects the inside of the control disk 8. If the playbetween the control disk 8 and the inside of the edge 19 is small thecup 3 can be dispensed with, as a damping action takes place between thecontrol disk 8 and the special baffle 20.

Turning to FIG. 4, there is shown a pressure independent valve with allparts identical to the FIG. 1, including cup 3 has been added and aspecial baffle 20, as in FIG. 3, is used. The special baffle 20 has anedge 19 on the perimeter of the baffle 20. It faces downward and has aninside diameter slightly larger than the control disk 8. This makes itpossible to fit the control disk 8 inside the edge 19. This protects theinside of the control disk 8 and a dashpot is formed, which togetherwith the cup 3 has to the effect that the pressure regulator isdampened, and the pressure independent valve is stabilized.

Turning to FIG. 5, there is seen a pressure independent valve with allparts identical to the FIG. 1, including cup 3 has been added and abaffle 13 is used but, instead of control disk 8, a special control disk21 is employed having an edge (flange) 22 on the perimeter of thecontrol disk 21. The edge 22 faces upward and has an inside diameterslightly larger than the baffle 13. This makes it possible to fit thebaffle 13 inside the edge 22, which protects the inside of the controldisk. A dashpot is formed by these components, which work together withthe cup 3 to provide the effect that the pressure regulator is dampened,and the pressure independent valve is stabilized.

The pressure independent valve can have the control valve after orbefore the differential regulator as described in United States PatentNo. 6,827,100. Turning to FIG. 6 there is seen a pressure independentvalve of the invention with the characterized valve 10 placed before thedifferential pressure regulator. In this embodiment, the pressureindependent valve includes an inlet 1 and outlet 16. The inlet 1communicates with the control valve 10, which can communicate with apressure chamber 2. From there the fluid passes through the seat 15 andcontrol disk 8 into the outlet 16. The control disk 8 is connected to adiaphragm 4 via a stem 17. The stem 17 is guided by a guide post 9. Thecontrol disk 8, stem 17 and diaphragm 4 can move as one unit. A cup 3with a center hole 18 for the stem 17 is placed over the cup 3 whichcovers the upper area of the diaphragm 4. The center hole 18 has adiameter only slightly larger than the stem 17, so a resistance to theflow of fluid between the diaphragm 4 and the pressure chamber 6. Thisdampens the reaction of the pressure regulator and leads to a morestabile function of the pressure independent valve. The pressure at theinlet 1 is via a reference channel 11 brought to the under side of thediaphragm 4 which is biased by a spring 5.

In the various embodiments of the invention, a cup 3, a baffle 13 or 20or a control disk 21 can be used singly or in combination. FIGS. 1, 2, 4and 6 show different versions of a valve according to the inventionwherein a cup 3 has been added over the diaphragm area of a valve of thetype employing a differential pressure regulator and a characterizedvalve. The cup has a hole in the center for the spindle. The hole hasslightly larger diameter than the spindle. The volume under thediaphragm is in communication with a reference pressure located eitherupstream or downstream of the valve, depending upon the type of thevalve.

It is of particular advantage that the diaphragm can be enclosed by acup or similar device to provide improved response with limited hunting.The volume on top of the diaphragm is enclosed by the cup. Fluid fromthe inlet or outlet can communicate with the enclosed volume through arestriction. It can be in the form of the play between the spindle andthe hole. The restriction is the leakage between the two. Or, it can bea very tight play between the spindle and the hole in the cup, so therewill be a very small leakage and then use a very fine opening in the cupas a restriction. However, the first alternative is preferred.

The cup described above has advantageous effect that the short termpressure variations over the valve and thereby the diaphragm can beattenuated. This improves the stability of the differential pressureregulator and can eliminate the hunting that otherwise can occur whenthe pressure and the flow is getting too high.

The flow of fluid is controlled by a control disk and a seat in thedifferential pressure regulator. It is another advantage of theinvention that this control disk can be shielded by a baffle or shield,mounted over the top of the control disk so that it is covered andprotected from downward jets of fluid. These downward jets of fluid arecaused by fluid flowing from the periphery of the control disk and theseat of the differential regulator hitting the wall of the regulator andmoving back against the top of the control disk. It is an advantage ofthe invention that the baffle prevents the jets from impacting thecontrol disk so the force balance of the control disk is not influenced.

It is an advantage of the invention that the baffle enhances theaccuracy of the pressure independent valve, especially at higher flows.The baffle is preferably firmly attached to the wall or guide past ofthe valve body.

The bottom part of the baffle is situated just slightly above thehighest position of the movement of the control disk. This provides thebenefit that water can pass between the top side of the baffle and thewall of the differential pressure regulator. In a preferred form, thehebaffle is a disk with a stand off that also works as a fastening device.The fastening device can attach to the wall of the valve body or to theguide post.

The baffle can be a simple disk or have raised edges, so it forms acylindrical cup. The edges preferably face the control disk. If the edgehas a diameter slightly larger than the control disk, it can partiallyoperate inside the baffle and a damping mechanism has been accomplished.

As an alternative, the control disk can have raised edges, so that itforms a cylindrical cup. In this case the edges face the baffle. If theedges have a diameter slightly larger than the baffle so that it canpartially operate inside the control disk and a damping mechanism hasbeen accomplished.

The above description is intended to enable the person skilled in theart to practice the invention. It is not intended to detail all of thepossible modifications and variations that will become apparent to theskilled worker upon reading the description. It is intended, however,that all such modifications and variations be included within the scopeof the invention that is seen in the above description and otherwisedefined by the following claims and, in some instances, some features ofthe invention will be employed without the corresponding use of theother features. The claims are meant to cover the indicated elements andsteps in any arrangement or sequence that is effective to meet theobjectives intended for the invention, unless the context specificallyindicates the contrary.

1. A pressure independent fluid flow regulating valve providing asubstantially constant flow rate for each set position, comprises: aflow passage leading to a characterized valve having an inlet from andan outlet to said flow passage; upstream of said characterized valve, aseat orifice intersecting said flow passage; a moveable assembly,comprising a disk connected to by a stem, and operated by a pressuresensing means; wherein the disk is located downstream of the seat withwhich it interacts to vary the flow resistance, and the effectivesurface area of the disk is essentially the same as the effectivesurface area of said pressure sensing means; downstream of the disk, abaffle is mounted in a fixed position, close to the disk but at adistance permitting the movement of the disk; the pressure sensing meansoperates inside a cylinder or chamber which it divides in two portions,wherein one portion is connected to the inlet, and the other portion isconnected via reference pressure passage to a point downstream of thecharacterized valve; and spring means for biasing said moveableassembly.
 2. A pressure independent fluid flow regulating valveproviding a substantially constant flow rate for each set position,comprises: a flow passage leading to a characterized valve having aninlet from and an outlet to said flow passage; upstream of saidcharacterized valve, a seat orifice intersecting said flow passage; amoveable assembly, comprising a disk connected to by a stem, a pressuresensing means comprising a diaphragm and a cup positioned over andcovering the pressure sensing means; wherein the disk is locateddownstream of the seat with which it interacts to vary the flowresistance, and the effective surface area of the disk is essentiallythe same as the effective surface area of said pressure sensing means;the pressure sensing means operates inside a cylinder or chamber whichit divides in two portions, wherein one portion is connected to theinlet, and the other portion is connected via reference pressure passageto a point downstream of the characterized valve, and the cup includesan opening permitting fluid to flow between the chamber and the pressuresensing means to provide dampening; and spring means for biasing saidmoveable assembly.
 3. A pressure independent fluid flow regulating valveproviding a substantially constant flow rate for each set position,comprises: a flow passage leading to a characterized valve having aninlet from and an outlet to said flow passage; downstream of saidcharacterized valve, a seat orifice intersecting said flow passage; amoveable assembly, comprising a disk connected to, and operated by apressure sensing means; wherein the disk is located downstream of theseat with which it interacts to vary the flow resistance and theeffective surface area of the disk, is essentially the same as theeffective surface area of said pressure sensing means; downstream of thedisk, a baffle is mounted in a fixed position, close to the disk but ata distance permitting the movement of the disk; the pressure sensingmeans operates inside a cylinder or chamber which it divides in twoportions, one portion is connected to the throttling device, the otherportion via a reference pressure passage connected to a point upstreamof the characterized valve; and spring means biases said moveableassembly.
 4. A pressure independent fluid flow regulating valveproviding a substantially constant flow rate for each set position,comprises: a flow passage leading to a characterized valve having aninlet from and an outlet to said flow passage; downstream of saidcharacterized valve, a seat orifice intersecting said flow passage; amoveable assembly, comprising a disk connected to by a stem, a pressuresensing means comprising a diaphragm and a cup is placed over andcovering the pressure sensing means; wherein the disk is locateddownstream of the seat with which it interacts to vary the flowresistance, and the effective surface area of the disk is essentiallythe same as the effective surface area of said pressure sensing means;the pressure sensing means operates inside a cylinder or chamber whichit divides in two portions, wherein one portion is connected to theoutlet, and the other portion is connected via reference pressurepassage to a point upstream of the characterized valve, and the cupincludes an opening permitting fluid to flow between the chamber and thepressure sensing means to provide dampening; and spring means forbiasing said moveable assembly.
 5. Pressure independent valve accordingany of claims 1 or 3, wherein the baffle has an edge on the side facingthe disk.
 6. Pressure independent valve according any of claims 1 or 3,where the disk has an edge on the side facing the baffle.
 7. Pressureindependent valve according to any of claims 1 or 3, where a cup coversone side of the pressure sensing means and includes a small openingacting as a resistance to the fluid.
 8. Pressure independent valveaccording to claim 7, where the resistance to the fluid is in the formof the play between the cup and a spindle passing a hole in the clip.